The present invention relates to an electrophotography, and more particularly an electrophotographic apparatus for forming a plurality of duplicated copies from each of sheet-like documents.
General electrophotographic apparatuses are designed to form copies of thick documents such as books. When a sheet-like document is to be duplicated, the document is placed on a document table and is pressed down by means of a document cover and after that the document table and a projecting optical system are reciprocated relative to each other so as to effect an exposing and scanning.
On the other hand various electrophotographic apparatuses are known in which the sheet-like document is fed by feeding means such as rollers, belts and the like so as to be exposed and scanned. Such a sheet-like document feeding and exposing device has a simple and compact construction as compared with the above mentioned document table exposing device, because it is not necessary to provide a mechanism for driving reciprocally the document table or the projecting optical system. Moreover, in the sheet-like document exposing and scanning device it is not necessary to open and close the document cover for each document and it is sufficient only to insert the document into the device. Therefore it is quite convenient to obtain a single copy from each of a number of documents.
However, in the sheet-like document exposing and scanning device after the document has been scanned it is discharged out of the device and thus it is required to feed the same document repeatedly when a plurality of copies have to be formed. Therefore if a plurality (n) of copies are to be duplicated from each of a plurality (m) of sheetlike documents, these documents must be fed m.times.n times. This is very cumbersome as compared with the device in which the document table or the optical system is repeatedly reciprocated so as to obtain a plurality of copies from the same document. It is also known to provide a collator or sorter which can distribute automatically the duplicated copies into n sets of copies. However it is worthless to combine the sheet-like document exposing and scanning device with such a collator and thus there has not been developed such a combination.
At present various kinds of electrophotographic apparatus have been developed in which a plurality of identical copies can be duplicated on the basis of a single image-modulated pattern which has been once formed by a single optical scanning of a document to be copied. for example there have been proposed the following processes:
(1) an electrostatic charge latent image is formed on a photosensitive screen and a plurality of corresponding latent images are formed on a plurality of dielectric record medium with modulating a corona ion stream on the basis of said originally formed latent image;
(2) by using photosensitive material having a persistent internal conductive property due to fatigue of material, an optical image of the document is projected on this photosensitive material so as to form a pattern modulated with the optical image and then a charging step, a developing step and a transferring step are repeatedly carried out so as to form a plurality of identical duplicated copies;
(3) after an electrostatic charge latent image is formed on electrophotographic photosensitive material by carrying out a homogeneously charging step, an optical image projecting step, a developing step and a transferring step are periodically repeated in such a manner that the original latent image is not damaged so as to obtain a plurality of identical copies; and
(4) on a photosensitive layer there is formed electrophotographically an image pattern composed of different regions in ink receptive property, charge retentive property or light transmission property and then an ink development step and a transferring step; a corona charging step, a development step and a transfer step; or a corona charging step, a homogeneous irradiation step, a development step and a transfer step are repeatedly effected so as to form a plurality of copies.